In an IC, LSI, or other semiconductor device and a semiconductor device in a liquid crystal display, aluminum, aluminum alloy, or another conductive metal and SiO2 or other insulating film are formed on a silicon substrate or glass substrate, a photoresist is uniformly coated, then a resist pattern is formed by a photolithographic process, the conductive metal and the insulating film are dry-etched using the pattern as a mask, then the unnecessary resist is stripped off to form the microcircuit.
Recently, along with the increasingly higher integration and densities of integrated circuits, super miniaturization has become demanded. Extensive use is therefore being made of the method of performing sophisticated dry etching, then stripping off the unnecessary resist by plasma ashing. Due to the dry etching and the ashing treatment, resist residue is left at the side walls, bottom, etc. of the patterns. If the resist residue is not completely stripped off, problems occur such as a reduced yield.
As the prior art for stripping off the resist residue, a stripper based on a fluorocompound (see Japanese Unexamined Patent Publication (Kokai) No. 7-201794, Japanese Unexamined Patent Publication (Kokai) No. 8-202052, and Japanese Unexamined Patent Publication (Kokai) No. 11-271985), an amine-based stripper containing hydroxylamine (see U.S. Pat. No. 5,334,332), a stripper based on a quaternary ammonium compound (see Japanese Unexamined Patent Publication (Kokai) No. 7-247498), etc. may be mentioned. However, with these strippers, various defects are observed such as a low removal power of the resist residue weak or corrosiveness with respect to various types of interconnect materials and insulating films. Therefore, a high functional stripper which is able to handle super miniaturization, that is, has a high removal power of the resist residue and will not corrode various types of interconnect materials and insulating films, is being sought. In particular, at the present, the above problem is surfacing in aluminum alloy interconnects.
Aluminum alloy interconnects are generally formed by processing by dry etching using a resist patterned by lithography as a mask. After that, the remaining resist (resist residue) and reaction by-products formed by the dry etching (below, “polymer residue”) are removed by a stripper comprised of a chemical.
However, aluminum alloy interconnects made finer along with the increasingly high integration of semiconductor integrated circuits are corroded or etched by such a stripper. Along with this phenomenon, the line resistance is observed to increase. This phenomenon is particularly observed with strippers based on fluorocompounds. Further, such a phenomenon is less frequent with amine-based strippers containing hydroxylamine or strippers based on quaternary ammonium compounds, however, the stripping performance of the resist residue or the polymer residue is insufficient. Moreover, there is a phenomenon where the etching action of other metals (material burying lower layer contact holes such as tungsten) is accelerated causing electrical short-circuits. Under these circumstances, application is difficult.
For example, if measuring the line resistance-yield characteristic for micro aluminum alloy interconnects, specifically dense interconnects of line and space dimensions of 0.22 μm/0.24 μm, it is learned that when using conventional chemicals, it is difficult to suppress the rise of the line resistance and ultimately the desired line resistance-yield characteristic cannot be secured. Of course, if forming interconnects under milder conditions, the extent of rise in the line resistance does not become a problem even in the prior art and consequently a good yield can be secured, but the more the interconnects are miniaturized, the more conspicuous the above problem becomes. Improvement is being awaited.
Further, for example, if measuring the relationship between contact chain resistance and yield by TEG (Test Element Group) in a borderless contact structure where locally dense and long aluminum interconnects and upper aluminum interconnects have a larger area than sparse lower contacts (structure where lower contacts are not covered by upper aluminum interconnects), it has been learned that with the above prior art, the desired rise in the contact chain resistance cannot be secured and in the end the yield cannot be secured.
The phenomenon is due to the post-treatment chemical for removing the resist after processing for forming the aluminum interconnects and the polymer residue produced during that processing. It is due to the “notching” phenomenon on local aluminum interconnects. It is surmised that this is due to the surface of the aluminum interconnects changing to alumina after the processing to form the aluminum interconnects and the post-treatment chemical etching this alumina and further etching the aluminum material itself. These micro “notches” grow to larger “notches” due to the migration of aluminum due to later heat treatment, so promote a drop in the yield in a process forming multilayer interconnects.